Patient Positioning Free
Patient positioning is an integral part of operative planning. It can prevent pressure-related injuries, expand the operative corridor using gravity retraction and minimize surgeon’s fatigue.
Patient positioning for surgery often does not receive the attention it deserves. Small openings leading to deep operative fields require ergonomic patient positions to ensure a precise operative trajectory.
Several principles can be crucial in determining appropriate patient positioning. Usually there is no single factor, but rather a combination of factors deciding the desired operative trajectory. The patient’s body habitus and the surgeon’s preferences play important roles in the final choice of position. The multifactorial decision-making process for choosing the appropriate position needs to be carefully planned and shared with all of the operating room team members so the room layout can be accordingly adjusted.
Ideally, the lesion should be the highest point in the operative field, but with the exceptions of some cortical and superficial lesions, this is often not feasible because gravity retraction can be exploited for mobilization of the overlying brain for deep-seated lesions. Furthermore, the exposed surface of the patient’s skull and perimeter of the craniotomy should preferably be parallel to the floor.
The torso should be positioned before the head, because head fixation by the skull clamp precludes further significant changes in the position of the torso, except for tilting or Trendelenburg and reverse Trendelenburg movements.
I prefer to use a skull clamp for almost all microsurgical procedures, and I reserve the use of padded doughnut and horseshoe-shaped clamps for nonmicrosurgical operations involving resection of superficial tumors and evacuation of primary hematomas.
The most appropriate patient operative position should:
- allow the least obstructed intradural trajectory toward the target lesion while minimizing risk of injury to the normal cerebrovascular structures,
- keep the patient as close to the physiological body position as possible to minimize pressure-related musculoskeletal and peripheral nerve injuries,
- enable the surgeon to maintain an ergonomic body posture to conduct relaxed microsurgical maneuvers in order to minimize surgeon’s fatigue.
If the patient is placed in an optimal position, the surgeon will have an opportunity to expand the operative corridor through safe mobilization of the cerebrum or cerebellum using gravity retraction. The extension of the patient’s head to mobilize the frontal lobe away from the anterior skull base during a pterional craniotomy is an example of this principle. In addition, an optimum head position can improve visualization of the deep operative field by clearing blood through gravity. The lateral head position used during a suboccipital craniotomy illustrates this point.
Surgeon’s fatigue is often under-recognized, but it can be a crucial factor in outcome during lengthy operations on skull base tumors and arteriovenous malformations. An inappropriate position of the patient’s head or an inadequate armrest can force the surgeon to assume an awkward arm posture that results in hand tremor. This can cause the surgeon to lose composure and patience during the later critical parts of the operation. For example, the surgeon should use an armrest during a supracerebellar craniotomy when the patient is in the park-bench position.
I prefer to sit during the microsurgical intradural part of surgery. I use only two distinct patient positions for nearly 90% of my operations. I use the supine position for lesions located from the nose up to the level of the parietal eminence (bossing). I use the modified park-bench position (often referred to as the “lateral” or “lateral oblique” position in this Atlas) for lesions located from the parietal eminence to the occipitocervical junction.
The other 10% of my cases require the patient to be placed in a sitting or prone position. The sitting position is used for surgeries on pineal region masses in morbidly obese patients, and the prone position is used for emergency posterior fossa cases since it can be arranged more expeditiously than the park-bench position.
The supine position is used for endoscopic transnasal, pterional, frontal, temporal, interhemispheric, and anterior parietal craniotomies. I also use the supine position for anterior and middle skull base osteotomies.
The modified park-bench position is ideal for posterior parietal, occipital, all posterior fossa and posterior skull base corridors, and craniocervical junction operations. I avoid placing patients in the supine position for posterior fossa operations since the neck torsion required for the operative head position is nonphysiologic. This neck posture may cause significant postoperative neck pain.
Patients with significant cervical degenerative stenotic changes or morbid obesity are best served in the modified park-bench position if any moderate neck turn is necessary. Patients with lesions near the parietal eminence are also frequently placed in the modified park-bench position.
The patient’s arms and legs should be positioned in anatomically neutral/slightly flexed positions and all bony prominences should be well padded.
The supine position is flexible and can be adjusted to cater to a number of anterior and middle fossa craniotomies. Foam cushions, gel pads, pillows, and padded armrests are advised.
For further details about the supine position and corresponding incisions, please refer to the chapter on Scalp Incisions.
Lateral Oblique or Park-Bench Position
This position is adaptable by tilting the table. I like this position because it allows me to keep the patient in a relatively physiologic posture while I am seated during the microsurgical portion of the posterior fossa operations. The patient’s neck is flexed and an “armored endotracheal tube” is used to avoid kinking of the tube during neck flexion. Neck flexion should leave at least two-fingers width between the patient’s chin and chest (thyromental distance).
I have had my own share of learning experiences with patient positioning. For example, I did not mobilize the shoulder of one obese patient effectively and faced an impossible task of working through the supracerebellar transtentrorial approach to remove a petrous apex meningioma. In this case, the patient’s shoulder obstructed my inferior-to-superior operative trajectory.
There are clear advantages to placing the patient in the sitting position. The surgeon’s visualization is improved through the dry and clear operative field associated with this position, and gravity assists with cerebellar retraction. Resection of acoustic neuromas with the patient in the sitting position can be advantageous because of a clear operative field and use of atraumatic bimanual dissection around the facial nerve. Because gravity keeps the field clear, intermittent irrigation minimizes the use of the suction apparatus around the brainstem and cranial nerves, so these structures may undergo less traumatic manipulation.
The sitting position can be potentially beneficial for morbidly obese patients undergoing posterior fossa operations. Cranial venous drainage and ventilation may be significantly compromised when the prone or park-bench position is used for these patients.
However, there are numerous drawbacks to the sitting position that have restricted its use to only select patients. Venous air embolism can be life threatening and is a real risk when the patient is in this position. Other rare complications include subdural hematoma, brachial plexus injury, cervical quadriplegia, and sciatic nerve injury. Operator’s hand fatigue and unsteady arm positions are problematic. Also, the preparations for placing the patient in the sitting position can lengthen operative times.
All of the assistants and surgical technicians who handle the instruments should have adequate access to the monitors that show the view of the operative field through the microscope.
Prolonged pressure on the radial nerve in the spiral groove of the humerus, on the ulnar nerve at the epicondylar groove, and on the peroneal nerve at the fibular head should be avoided.
Pearls and Pitfalls
- The appropriate position, most importantly, should allow the least obstructed intradural trajectory to reach the target lesion while minimizing risk of injury to the normal cerebrovascular structures.
- The lateral or modified park-bench position is a versatile and obviates the need to place the patient in the prone position. It also allows the operator to sit during microsurgery.
- Numerous factors should be considered for selection of the final position. The use of ”rigid” protocols to streamline the decision-making process for selection of the suitable position should be avoided.
- Gravity can facilitate expansion of the operative corridor and should be exploited.
- The surgeon comfort is important, especially during long operations.
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